Delivery systems

ABSTRACT

A delivery system comprising a covering containing at least a first substance for release to a surgical site is provided. The covering includes an elongated containment portion having at least one compartment, wherein the covering retains the first substance for mixing with a second substance prior to delivery at a surgical site. The covering may be a single or multi compartment structure capable of retaining at least partially the mixture of the at least first and second substances until the covering is placed at the surgical site. The elongated containment portion of the covering includes a first end and second end opposite each other, wherein at least one end defines an access port configured to receive a device capable of delivering a second substance into the elongated containment portion for mixing with the first substance prior to or during the surgical procedure.

FIELD

A delivery system for delivering a substance or material to a surgical site is provided. More particularly, a delivery system comprising a covering and a substance, the covering being configured for at least partially retaining the substance provided therein until the delivery system is placed at a surgical site.

BACKGROUND

The use of bone grafts and bone substitute materials in orthopedic medicine is known. While bone wounds can regenerate without the formation of scar tissue, fractures and other orthopedic injuries take a long time to heal, during which time the bone is unable to support physiologic loading unaided. Metal pins, screws, rods, plates and meshes are frequently required to replace the mechanical functions of injured bone. However, metal is significantly more stiff than bone. Use of metal implants may result in decreased bone density around the implant site due to stress shielding. Physiologic stresses and corrosion may cause metal implants to fracture. Unlike bone, which can heal small damage cracks through remodeling to prevent more extensive damage and failure, damaged metal implants can only be replaced or removed. The natural cellular healing and remodeling mechanisms of the body coordinate removal of bone and bone grafts by osteoclast cells and formation of bone by osteoblast cells.

Conventionally, bone tissue regeneration is achieved by filling a bone repair site with a bone graft. Over time, the bone graft is incorporated by the host and new bone remodels the bone graft. In order to place the bone graft, it is common to use a monolithic bone graft or to form an osteoimplant comprising particulated bone in a carrier. The carrier is thus chosen to be biocompatible, to be resorbable, and to have release characteristics such that the bone graft is accessible.

The rapid and effective repair of bone defects caused by injury, disease, wounds, or surgery is a goal of orthopedic surgery. Toward this end, a number of compositions and materials have been used or proposed for use in the repair of bone defects. The biological, physical, and mechanical properties of the compositions and materials are among the major factors influencing their suitability and performance in various orthopedic applications.

Demineralized bone matrix (DBM) implants have been reported to be particularly useful. Demineralized bone matrix is typically derived from cadavers. The bone is removed aseptically and/or treated to kill any infectious agents. The bone is then particulated by milling or grinding and then the mineral components are extracted for example, by soaking the bone in an acidic solution.

Current DBM formulations have various drawbacks. First, while the collagen-based matrix of DBM is relatively stable, the active factors within the DBM matrix are rapidly degraded. The osteogenic activity of the DBM may be significantly degraded within 24 hours after implantation, and in some instances the osteogenic activity may be inactivated within 6 hours. Therefore, the factors associated with the DBM are only available to recruit cells to the site of injury for a short time after transplantation. For much of the healing process, which may take weeks to months, the implanted material may provide little or no assistance in recruiting cells.

Attempts to overcome these problems have lead researchers to utilize delivery systems such as polymer mesh bags to release DBM at a surgical site. However, any additional bone graft material, such as autologous bone or growth factors, would have to be placed underneath or on top of the DBM mesh bag, which approach does not induce new bone formation.

Thus, there is a need to improve the efficacy and consistency of DBM delivery systems by mixing the DBM particles/fibers with other bone graft materials such as autologous bone and other bioactive agents throughout the mesh bag prior to or during the surgical procedure. It would therefore be desirable to provide delivery systems that are configured to get live cells and other bioactive agents in close contact with DBM particles/fibers so as to induce bone growth throughout the graft material rather than primarily along the surface of the DBM containing polymer mesh bag.

SUMMARY

A delivery system for delivering a substance or material to a surgical site is provided. The delivery system comprises a covering and a substance to be retained within and delivered by the covering. Generally, the covering may be a single or multi-compartment structure capable of at least partially retaining a substance provided therein until the covering is placed at a surgical site. In some examples, upon placement, the covering facilitates transfer of the substance and/or materials from the covering to the surgical site. The covering may participate in, control, or otherwise adjust, the release of the substance or penetration of the covering by surrounding materials, such as cells or tissues.

In some embodiments, the covering of the delivery system includes an elongated containment portion having at least one compartment and at least a first substance which is retained for mixing with a second substance prior to delivery at a surgical site. The first substance can be particles, fibers or chips of demineralized bone matrix (DBM) and the second substance can be bone graft material such as autologous milled bone particles and/or growth factors.

In some embodiments, the elongated containment portion has a cross sectional shape selected from generally circular or generally oval and a shape that can be tubular, rectangular, or cubic. The covering can have two ends opposite each other and be made from porous mesh to provide, for example, a porous mesh bag.

In various embodiments, each end of the elongated containment portion can define at least one access port configured to receive the needle of a syringe or another means of delivering osteogenic bone graft material. The syringe has a plunger which is adapted to release the bone graft material into the at least one compartment. As the plunger is pushed toward the needle and the needle is extracted from the elongated containment portion of the delivery system, DBM becomes mixed with bone graft material. The first end or the second or both ends of the elongated containment portion are configured to be sealed by a sealing mechanism, such as for example, a draw string, sutures, heat seals or a combination thereof.

In other embodiments, a face of the covering may define at least one access port or a thru hole through which bone graft material can be introduced into the delivery systems prior to or during the surgery. After the bone graft material is added to the covering, each access port or thru hole can self seal or be sealed.

In some embodiments, either the first end or the second end or both ends of the elongated containment portion are configured to receive a funnel adapted to channel bone graft material into the containment portion of the delivery system. In some embodiments, the delivery system further comprises a stand for use in supporting the elongated containment portion while it receives bone graft material through the funnel or any other device used for filling the delivery systems described herein with bone graft materials.

In various embodiments, the delivery device can be filled with the bone graft material and a second substance including a protein (e.g., bone morphogenetic proteins), carbohydrates, lipids, collagen, allograft bone, autograft bone, tricalcium phosphate, hydroxyapatite, growth and differentiation factors, bone promoting substance, carriers for growth factors, growth factors extracts of tissue, bone marrow aspirate, concentrates of lipid derived or marrow derived adult stem cells, umbilical cord derived stem cells, committed or partially committed cells from osteogenic or chondrogenic lineage, antimicrobials, antibiotics, or combinations thereof.

In certain embodiments the elongated containment portion of the delivery system includes multi compartments that can be arranged side by side or over each other. Each compartment is separated from the others by partitions or barriers that can be temporary or permanent.

In some embodiments, some of the compartments of the device are unfilled at manufacture but can be configured to be filled prior to or during the surgical procedure.

Additional features and advantages of various embodiments will be set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practice of various embodiments. The objectives and other advantages of various embodiments will be realized and attained by means of the elements and combinations particularly pointed out in the description and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In part, other aspects, features, benefits and advantages of the embodiments will be apparent with regard to the following description, appended claims and accompanying drawings where:

FIG. 1 illustrates a side view of a delivery system comprising a covering having an elongated containment portion and two ends in accordance with one embodiment of the present disclosure;

FIG. 1A illustrates a side view of a delivery system comprising a covering such as a porous mesh bag having an elongated containment portion defining one access port in accordance with another embodiment of the present disclosure;

FIG. 2 illustrates a top view of a delivery system comprising a covering having an elongated containment portion defining two access ports in accordance with an embodiment of the present disclosure;

FIG. 3 illustrates a top view of a delivery system including a covering comprising an elongated containment portion defining three thru holes in accordance with another embodiment of the present disclosure;

FIG. 4 illustrates a top view of a delivery system comprising a covering having a channel running horizontally through the covering in accordance with an embodiment of the present disclosure;

FIG. 4A illustrates an end view of the covering shown in FIG. 4;

FIG. 5 illustrates a side view of a delivery system of FIG. 3, the delivery system comprising a covering having multi compartments situated side by side in accordance with another embodiment of the present disclosure;

FIG. 6 illustrates a side view of a delivery system of FIG. 4, the delivery system having a covering comprising a channel running horizontally through the covering in accordance with an embodiment of the present disclosure;

FIG. 7 illustrates an end view of a delivery system comprising a covering having two compartments in accordance with another embodiment of the present disclosure;

FIG. 8 illustrates an end view of a delivery system comprising a covering having three compartments in accordance with another embodiment of the present disclosure;

FIG. 9 illustrates an end view of a delivery system comprising a covering having three compartments in accordance with another embodiment of the present disclosure;

FIG. 10 illustrates an end view of a delivery system comprising a covering having two compartments in accordance with another embodiment of the present disclosure;

FIG. 11 illustrates a side view of a delivery system comprising a covering such as a mesh bag comprising a closed end and an open end that can be closed by draw strings 284 in accordance with another embodiment of the present disclosure;

FIG. 12 illustrates a top view of a delivery system comprising a mesh bag having an open end that can be closed by draw strings 284 in accordance with another embodiment of the present disclosure;

FIG. 13 illustrates a side view of a delivery system comprising a covering such as a mesh bag having a closed end and an open end that can be closed by draw strings 284, the open end adapted to receive a funnel in accordance with an embodiment of the present disclosure.

It is to be understood that the figures are not drawn to scale. Further, the relation between objects in a figure may not be to scale, and may in fact have a reverse relationship as to size. The figures are intended to bring understanding and clarity to the structure of each object shown, and thus, some features may be exaggerated in order to illustrate a specific feature of a structure.

DETAILED DESCRIPTION

For the purposes of this specification and appended claims, unless otherwise indicated, all numbers expressing quantities of ingredients, percentages or proportions of materials, reaction conditions, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding the numerical ranges and parameters set forth herein, the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Moreover, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a range of “1 to 10” includes any and all subranges between (and including) the minimum value of 1 and the maximum value of 10, that is, any and all subranges having a minimum value of equal to or greater than 1 and a maximum value of equal to or less than 10, e.g., 5.5 to 10.

Reference will now be made in detail to certain embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the illustrated embodiments, it will be understood that they are not intended to limit the invention to those embodiments. On the contrary, the invention is intended to cover all alternatives, modifications, and equivalents that may be included within the invention as defined by the appended claims.

The headings below are not meant to limit the disclosure in any way; embodiments under any one heading may be used in conjunction with embodiments under any other heading.

Definitions

It is noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the,” include plural referents unless expressly and unequivocally limited to one referent. For example, reference to “a compartment” includes one, two, three or more compartments.

Bioactive agent or bioactive compound, as used herein, refers to a compound or entity that alters, inhibits, activates, or otherwise affects biological or chemical events. For example, bioactive agents may include, but are not limited to, osteogenic or chondrogenic proteins or peptides, anti-AIDS substances, anti-cancer substances, antibiotics, immunosuppressants, anti-viral substances, enzyme inhibitors, hormones, neurotoxins, opioids, hypnotics, anti-histamines, lubricants, tranquilizers, anti-convulsants, muscle relaxants and anti-Parkinson substances, anti-spasmodics and muscle contractants including channel blockers, miotics and anti-cholinergics, anti-glaucoma compounds, anti-parasite and/or anti-protozoal compounds, modulators of cell-extracellular matrix interactions including cell growth inhibitors and antiadhesion molecules, vasodilating agents, inhibitors of DNA, RNA or protein synthesis, anti-hypertensives, analgesics, anti-pyretics, steroidal and non-steroidal anti-inflammatory agents, anti-angiogenic factors, angiogenic factors, anti-secretory factors, anticoagulants and/or antithrombotic agents, local anesthetics, ophthalmics, prostaglandins, anti-depressants, anti-psychotic substances, anti-emetics, and imaging agents. In certain embodiments, the bioactive agent is a drug. In some embodiments, the bioactive agent is a growth factor, cytokine, extracellular matrix molecule or a fragment or derivative thereof, for example, a cell attachment sequence such as RGD. A more complete listing of bioactive agents and specific drugs suitable for use in the present invention may be found in “Pharmaceutical Substances: Syntheses, Patents, Applications” by Axel Kleemann and Jurgen Engel, Thieme Medical Publishing, 1999; the “Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals”, Edited by Susan Budavari et al., CRC Press, 1996; and the United States Pharmacopeia-25/National Formulary-20, published by the United States Pharmcopeial Convention, Inc., Rockville Md., 2001, each of which is incorporated herein by reference.

Biocompatible, as used herein, refers to materials that, upon administration in vivo, do not induce undesirable long-term effects.

Bone, as used herein, refers to bone that is cortical, cancellous or cortico-cancellous of autogenous, allogenic, xenogenic, or transgenic origin.

Demineralized, as used herein, refers to any material generated by removing mineral material from tissue, e.g., bone tissue. In certain embodiments, the demineralized compositions described herein include preparations containing less than 5% calcium and preferably less than 1% calcium by weight. Partially demineralized bone (e.g., preparations with greater than 5% calcium by weight but containing less than 100% of the original starting amount of calcium) is also considered within the scope of the invention. In some embodiments, demineralized bone has less than 95% of its original mineral content. Demineralized is intended to encompass such expressions as “substantially demineralized,” “partially demineralized,” and “fully demineralized.”

Demineralized bone matrix, as used herein, refers to any material generated by removing mineral material from bone tissue. In preferred embodiments, the DBM compositions as used herein include preparations containing less than 5% calcium and preferably less than 1% calcium by weight. Partially demineralized bone (e.g., preparations with greater than 5% calcium by weight but containing less than 100% of the original starting amount of calcium) are also considered within the scope of the invention.

Osteoconductive, as used herein, refers to the ability of a non-osteoinductive substance to serve as a suitable template or substance along which bone may grow.

Osteogenic, as used herein, refers to the ability of an agent, material, or implant to enhance or accelerate the growth of new bone tissue by one or more mechanisms such as osteogenesis, osteoconduction, and/or osteoinduction.

Osteoimplant, as used herein, refers to any bone-derived implant prepared in accordance with the embodiments of this invention and therefore is intended to include expressions such as bone membrane, bone graft, etc.

Osteoinductive, as used herein, refers to the quality of being able to recruit cells from the host that have the potential to stimulate new bone formation. Any material that can induce the formation of ectopic bone in the soft tissue of an animal is considered osteoinductive. For example, most osteoinductive materials induce bone formation in athymic rats when assayed according to the method of Edwards et al., “Osteoinduction of Human Demineralized Bone: Characterization in a Rat Model,” Clinical Orthopaedics & Rel. Res., 357:219-228, December 1998, incorporated herein by reference.

Superficially demineralized, as used herein, refers to bone-derived elements possessing at least about 90 weight percent of their original inorganic mineral content, the expression “partially demineralized” as used herein refers to bone-derived elements possessing from about 8 to about 90 weight percent of their original inorganic mineral content and the expression “fully demineralized” as used herein refers to bone containing less than 8% of its original mineral context.

Introduction

A delivery system for delivering a substance or material to a surgical site is provided. In various embodiments, the delivery system comprises a covering and a substance for delivery by the covering. The covering provides a superior containment of the substance, such as graft material, which helps focus and concentrate materials that provide healing at the surgical site. In some embodiments, the covering also helps the surgeon perform less invasive procedures, by delivering a contained unit of grafting material to the surgical site.

The delivery system may be used to treat a wide variety of bone or soft tissue defects including surgically created or pre-existing (such as by trauma) defects. In some embodiments, the delivery system may be used to treat contained bony voids or contained defects. Such bony voids are voids or cavities that have a cortical shell on three sides. In some embodiments, the delivery system may be used to treat critical defects. Generally, critical defects are defects that will not heal spontaneously and must be grafted in order to assure healing. In some embodiments, the delivery system may be used to treat segmental defects. Segmental defects are defects in the cortical shaft of a long bone in which a segment is missing. In some embodiments, the delivery system may be used to treat contained or non-critical defects wherein the delivery system may act as a plug to assist healing. Other applications for the delivery system are discussed herein and none are intended to be limiting.

The delivery system comprises a covering and a substance wherein the substance is provided within the covering for delivery to the surgical site. The delivery system provides increased handling properties, ability to place grafting material reliably using minimally invasive procedures, and improved delivery characteristics such as graft retention compared with other systems. In some embodiments, upon placement, the covering facilitates transfer of the substance and/or materials to the surgical site. In some embodiments, for example wherein the covering holds graft materials, the covering substantially prevents graft migration. The covering may participate in, control, or otherwise adjust, the release of the substance from the covering or penetration of the covering by surrounding materials, such as cells or tissues.

Generally, the covering may be a single or multi-compartment structure capable of at least partially retaining a substance provided therein until the covering is placed at a surgical site. In some embodiments, the covering may be substantially non-expandable or minimally deformable. In some embodiments, the covering may be a temporary covering wherein the covering is substantially resorbable. For example, in some embodiments, the covering may be formed of a material that is substantially resorbed within 2 weeks, within 4 weeks, within 12 weeks, or within other suitable time frame. Accordingly, in some embodiments a delivery system including the covering may be a temporary delivery system. The covering may include one or more attachment mechanisms for retaining the covering at the surgical site. The attachment mechanism may be a mechanical attachment mechanism, a physical attachment mechanism, a biological attachment mechanism or a chemical attachment mechanism, or may employ combinations of these. The attachment mechanism may be used to attach the covering to skeletal or soft tissue proximate the surgical site.

In some embodiments, the covering may be used for containment of particulate or morselized materials (the substance provided in the covering), optionally to provide a focus or concentration of biological activity. In some embodiments, the covering may be used for containment of a substance one or more of bone particles, bone fibers, other osteoinductive or osteoconductive materials, BMP, antibiotics, or other materials.

In some embodiments, the covering may be used for maintaining materials (the substance provided in the covering) in spatial proximity to one another, possibly to provide a synergistic effect. In some embodiments, the covering may be used to control availability of a substance provided within the covering to cells and tissues of a surgical site over time. In some embodiments, the covering may be used for delivery through a limited opening, such as in minimally invasive surgery or mini-open access. In some embodiments, the covering may be used to deliver morselized or particulated materials (the substance provided in the covering) in pre-measured amounts. In other embodiments, the substance may be liquid or flowable, or combinations of these with particulate, morselized, and/or other materials.

In various embodiments, the covering may contain a substance or material such as a graft material. The covering limits, and in some embodiments eliminates, graft migration and maintains graft density. The delivery system, with contained substance or material, may be configured to conform to surrounding bony contours or implant space. In some embodiments, the delivery system provides a pathway for healing/cell penetration and tissue ingrowth. Thus, the covering may facilitate transfer or diffusion of materials into and out of the covering. For example, the covering may facilitate diffusion of a substance out of the covering or may facilitate diffusion into the covering of materials in the surgical site, such as cells and tissues. The covering may be configured to permit diffusion of some materials while substantially preventing diffusion of other materials. Further, in various embodiments, the covering may be configured such that diffusion is permitted into or out of certain portions of the covering but not other portions of the covering. In some embodiments, the covering may merely retain a substance at the surgical site.

The covering may have a single compartment or may have a plurality of compartments. Thus, in one embodiment, the covering has a dual-compartment and comprises first and second compartments. A first substance may be provided in the first compartment and a second substance may be provided in the second compartment. The second compartment may be adjacent to, apart from, inside, or surrounding the first compartment. Materials forming the first compartment and the second compartment may be the same or may be different. Selection of materials, positioning of the compartments, and other factors relating to the first and second compartments may be chosen to achieve simultaneous or sequential delivery or release of a substance or substances.

Covering Material

The covering may comprise a structural material and, in some embodiments, a functional material. The structural material may comprise a mesh material, a polymeric material, a substantially solid material, or other structural material. The functional material may comprise, for example, a radiopaque material, a bacteriocidal material, or other functional material.

In various embodiments, in accordance with the specific application for which the covering is being used, the covering may be rigid, may be flexible, may be non-elastic, or may be elastic. The covering material may be braided, woven, non-woven shape memory, particulate, threaded, porous, non-porous, or substantially solid. While the term “structural” is used to describe the material forming the main structure of the covering, it is to be appreciated that this is not intended to imply that the covering need have structural or load-bearing characteristics.

The covering may participate in, control, facilitate, prevent, or otherwise adjust the release of the substance. For example, the covering may act as a selectively permeable membrane and/or may be porous, with the level of porosity being related to the nature of the substances inside the covering. Thus, the material for and configuration of the covering may be selected or adjusted based on desired release characteristics. Specific properties of the structural material that may be adjusted include thickness, permeability, porosity, strength, flexibility, elasticity, and others. It is to be appreciated that some of these properties may depend on others. For example, the thickness and porosity of the material may contribute to its strength, flexibility, and elasticity. In some embodiments, the covering may be made of a squishy, moldable, sticky, and/or tacky material to facilitate placement and packing of the covering.

In some embodiments, the covering may be porous to fluid like in consistenct, may be biocompatible, and may be resistant to rupture (including the time when the substance provided therein swells). In some embodiments, the covering with the substance provided therein may be load-bearing. The covering may be resorbable or non-resorbable. The covering may provide increased handling properties, may have irrigation resistance, may have material retention characteristics, and/or may support cellular penetration. Flexibility of the covering may be selected to suit particular applications. In some applications, it may be desirable to have a flexible covering. For example, the covering can be flexible enough to fold back on itself.

If the covering is made from a resorbable material, the covering degrades and disappears after a period of time. The covering thus may be considered a temporary covering. If the covering is not made of a resorbable material, the covering remains in the body. Tissue ingrowth may occur to bind the host tissue to the substance provided within the covering. Tissue ingrowth through and around the covering, between the host tissue and the substance provided within the covering, may be promoted via openings in the covering.

In various embodiments, the covering may comprise a porous material or a mesh material. The size of the pores of the covering may be designed to permit cellular infiltration (approximately several microns to several millimeters), but may also be designed specifically to exclude cells from the inside of the covering (e.g. approximately 0.45 microns) and only allow diffusion of small molecules (proteins and hormones). Thus, the covering may act to control access to the interior of the delivery system by cells. U.S. Patent Application Publication No. 2005/0283255 for Tissue-Derived Mesh for Orthopedic Regeneration describes suitable manners for forming a mesh for use with a covering as provided herein and is herein incorporated by reference in its entirety.

The covering may be formed of a resorbable or nonresorbable, natural or synthetic, biocompatible material. In some embodiments, more than one material may be used, including as multiple layers. For example, in an embodiment comprising two compartments, one or more materials may be used for the first compartment and a different material or materials may be used for the second compartment. For example, one compartment or portions thereof may be made of material or materials that provide a desired property or properties relative to other compartments or portions thereof, such as increased or decreased resorbability or stiffness, or the different compartments or portions thereof may be imparted with different drug delivery properties. Alternatively, all compartments may comprise the same material or mixtures of materials. Where the characteristics of the material are varied between compartments or over the surface of a single compartment, the pores of the first compartment or portion thereof may be larger than the pores of the second compartment.

The covering may comprise any suitable structure for delivering a substance in vivo. Thus, as described, the covering may comprise a mesh. In other embodiments, the covering may comprise a polymeric structure with a chamber provided therein. The chamber may be filled with a substance for delivering in vivo, such as autograft, demineralized bone matrix, or others disclosed herein.

In embodiments comprising more than one compartment, characteristics of the covering material may be varied between compartments. Generally, the porosity, flexibility, strength, or any other characteristic of one compartment may vary from that characteristic of the other compartment. Further, characteristics of the covering may vary at different positions of the covering regardless of compartmental configuration of the covering.

In some embodiments, the covering may expand when placed in the body. Expansion can be provided in at least two ways: the covering may be compressed such that the covering expands when placed in the body or the covering may be made of a material that expands when it comes in contact with water or other bodily fluids, either by way of liquid absorption, or by stretching when the materials inside it absorb liquid and themselves expand. In some embodiments, the covering may comprise a shape memory material such as copper-zinc aluminum-nickel alloy, copper-aluminum-nickel alloy, and nickel-titanium (NiTi) alloy. Reinforcing materials such as cortical bone, calcium phosphates, etc. may be incorporated into the structure of the covering to reinforce it. In other embodiments, the covering may be substantially non-expandable or minimally deformable.

The covering may be configured for specific compressive strength and rigidity by adjusting density and resorption time of the covering. In some embodiments, a coating may be provided over the covering. For example, the coating may be a compound of poly-L-lactide, of polyglycolic acid, or their polymers, or polyhydroxyalkanoates (polyhydroxybutyrates and polyhydroxyvalerates and copolymers). The coating may be selected such that it has a resorption time wherein it is resorbed by the body and the material within the covering is permitted to exit through openings in the covering.

Exemplary Covering Materials

Polymeric material (for example, see U.S. Pat. Nos. 6,696,073, 6,478,825, 6,440,444, and 6,294,187 and U.S. Patent Publications Nos. 2006/0216323 and 2005/0251267, all herein incorporated by reference in their entirety); woven material and braided material (for example, see U.S. Patent Publication No. 2005/0283255, herein incorporated by reference in its entirety); non-woven materials; shape memory material; porous materials; and non-porous materials may be used. In some embodiments, outer particles may be used to contain inner particles; particles may be attached to threads of material, and/or porosity may be added to mesh fibers. In some embodiments, materials may be used for portions of the covering, such as for a compartment of the covering, that are substantially impenetrable.

In some embodiments, the covering may comprise a mesh material. Suitable mesh materials include natural materials, synthetic polymeric resorbable materials, synthetic polymeric non-resorbable materials, and other materials. Natural mesh materials include silk, extracellular matrix (such as DBM, collagen, ligament, tendon tissue, or other), silk-elastin, elastin, collagen, and cellulose. Synthetic polymeric resorbable materials include poly(lactic acid) (PLA), poly(glycolic acid) (PGA), poly(lactic acid-glycolic acid) (PLGA), polydioxanone, PVA, polyurethanes, polycarbonates, polyhydroxyalkanoates (polyhydroxybutyrates and polyhydroxyvalerates and copolymers), polysaccharides, polyhydroxyalkanoates polyglycolide-co-caprolactone, polyethylene oxide, polypropylene oxide, polyglycolide-co-trimethylene carbonate, poly(lactic-co-glycolic acid), and others. See Chen and Wu, “The Application of Tissue Engineering Materials,” Biomaterials, 2005, 26(33): p. 6565-78, herein incorporated by reference in its entirety. Other suitable materials include carbon fiber, metal fiber, polyertheretherketones, non-resorbable polyurethanes, polyethers of all types, polyethylene terephthalte, polyethylene, polypropylene, Teflon, and various other meshes. In other embodiments, the covering may comprise non-woven material such as spun cocoon or shape memory materials having a coil shape or shape memory alloys. Alternatively, any of these materials may be used in a non-mesh form.

Generally, the covering may be formed of any natural or synthetic structure (tissue, protein, carbohydrate) that can be used to form a covering configuration. Thus, the covering may be formed of a polymer (such as polyalkylenes, for example, polyethylenes, polypropylenes), polyamides, polyesters, poly(glaxanone), poly(orthoesters), poly(pyrolicacid), poly(phosphazenes), polycarbonate, other bioabsorbable polymer such as Dacron or other known surgical plastics, a natural biologically derived material such as collagen, gelatin, chitosan, alginate, a ceramic (with bone-growth enhancers, hydroxyapatite), PEEK (polyether-etherketone), dessicated biodegradable material, metal, composite materials, a biocompatible textile (for example, cotton, silk, linen), extracellular matrix components, tissues, or composites of synthetic and natural materials, or other. Various collagen materials can be used, alone or in combination with other materials, including collagen sutures and threads. Some examples include polymer or collagen threads woven, or knitted, into a mesh. Other suitable materials include thin polymer sheets molded in the presence of a porogen and having underwent leaching; polymer sheets or naturally derived sheets such as fascia and other collagen materials, small intestinal submucosa, or urinary bladder epithelium, the sheets being punctured to introduce porosity; specific shapes printed using available or future printing technologies; naturally secreted materials such as bacterial cellulose grown within specific molds.

In some embodiments, mesh fibers may be treated to impart porosity to the fibers. This may be done, for example, to PLA, PLGA, PGA, and other fibers. One suitable method for treating the mesh fibers comprises supercritical carbon dioxide treatment to partially solubilize the particles. This treatment may further be carried out for viral inactivation. Another suitable method for treating the mesh fibers comprises explosive decompression. Explosive decompression generates porosity and leads to controlled permeability. The mesh material further may be loaded with cells, growth factors, or bioactive agents.

In further embodiments, fibers of a mesh material may be treated such as by having particles adhered thereto. The particles may be, for example, bone particles. Thus, in one embodiment, the covering may comprise a plurality of threads formed into a fabric. The threads may have particles adhered thereto. For example, the threads may have particles strung on the thread. In an alternative embodiment, the covering may be formed of a material and the material may be coated with particles.

In yet other embodiments, the covering may comprise a non-porous material, which may be permeable. A non-porous material may be used for later (or delayed) delivery of a substance provided therein. Such substance may comprise, for example, cells, growth factors, or bone morphogenetic proteins. Accordingly, in one embodiment, a delivery system for delayed delivery of cells, growth factors, or bone morphogenetic proteins is provided comprising a non-porous covering.

While certain embodiments are described with respect to having mesh characteristics, it is to be appreciated that not all embodiments may have such mesh characteristics. Further, the material used for the covering and its characteristics may be selected for specific applications. For example, in some embodiments, the covering may be formed of a resorbable material, such as formed as a resorbable container or capsule. Such resorbable material may be useful in delivering, for example, antibiotic to a site by an outer resorbable material, and then gradually exposing inner graft material after the infection is cleared. In such embodiments, the delivery system comprises a temporary delivery system.

Functional Material Characteristics

The covering material may have functional characteristics. Alternatively, other materials having functional characteristics may be incorporated into the covering. Functional characteristics may include radiopacity, bacteriocidity, source for released materials, tackiness, or a combination thereof. Such characteristics may be imparted substantially throughout the covering or at only certain positions or portions of the covering.

Suitable radiopaque materials include, for example, ceramics, mineralized bone, ceramics/calcium phosphates/calcium sulfates, metal particles, fibers, iodinated polymer or mixtures thereof. Other techniques for incorporating a biocompatible metal or metal salt into a polymer to increase radiopacity of the polymer may also be used. Suitable bacteriocidal materials may include, for example, trace metallic elements. In some embodiments, trace metallic elements may also encourage bone growth.

Functional material, such as radiopaque markers, may be provided at one or more locations on the covering or may be provided substantially throughout the covering. Thus, for example, in a tubular covering, a radiopaque marker may be provided at a tip of the tubular covering. Such marker may facilitate placement of the covering. Radiopaque materials may be incorporated into the covering and/or into the substance for delivery by the covering. Further, radiopaque materials may be provided at only some locations on the covering such that visualization of those locations provides indication of the orientation of the covering in vivo.

The covering itself may be designed to release materials during degradation of the covering material. Thus, bone morphogenic proteins (BMPs), growth factors, antibiotics, angiogenesis promoting materials (discussed more fully below), bioactive agents (discussed more fully below), or other actively releasing materials may be incorporated into the covering material such that as the covering material is degraded in the body, the actively releasing material is released. For example, an actively releasing material may be incorporated into a biodegradable polymer covering such as one manufactured of a biodegradable polyester such as poly(lactic acid) (PLA), poly(glycolic acid) (PGA), poly(lactic-co-glycolic acid) (PLGA), or polyhydroxyalkanoates (polyhydroxybutyrates and polyhydroxyvalerates and copolymers). In some embodiments, poly(ethylene glycol) (PEG) may be incorporated into the biodegradable polyester to add hydrophilic and other physico-chemical properties to enhance drug delivery. In some embodiments, composites of allograft bone and biodegradable polymers (for example, PLEXUR™ products available from Osteotech) may be used in the covering.

In some embodiments, the covering may comprise a material that becomes tacky upon wetting. Such material may be, for example, a protein or gelatin based material. Tissue adhesives, including mussel adhesive proteins and cryanocrylates, may be used to impart tackiness to the covering. In further examples, alginate or chitosan material may be used to impart tackiness to the covering. In further embodiments, an adhesive substance or material may be placed on a portion of the covering or in a particular region of the covering to anchor that portion or region of the covering in place at an implant site.

In one embodiment of a covering comprising two compartments, first and second materials may be used for the first and second compartments, respectively. The first material may release or expose a growth factor according to a first rate and the second material may release a growth factor according to a second rate. Further, the growth factors released by the first and second compartments may be the same or may be different. For example, an angiogenic growth factor may be provided with the first compartment and an osteoinductive growth factor may be provided with the second compartment.

Mesh Formulations

Any suitable technique may be used for forming a material for the covering. Generally, the material may be formed as a substantially solid material, as a sheet, as a mesh, or in other configuration. In some embodiments, the material may be a textile type material. Thus, for example, the material may be formed using a textile approach such as be weaving, rug making, knitting. Such formation may be by a mechanical or industrial method. In another embodiment, a substantially solid sheet may be formed and may be treated to assume a configuration penetrable by cells, fluids, and proteins. For example, the sheet may be perforated, may be expanded to create openings, or other. Also, it would be perfectly suitable to take a thin sheet of the covering material, and to perforate it, expand it to create openings, or otherwise make it penetrable by cells, fluids and proteins.

In one embodiment, elongated bone-derived particles or fragments of small intestinal submucosa may be combined longitudinally into three small bundles, each having, for example, from about 1 to about 3 tissue particles. The three bundles may then be braided. Various methods of braiding and types of braids any of which may be useful in producing the material of the invention herein are also described, for example, by Shaw, KNOTS—Useful & Ornamental, Bonanza Books, New York (1983), incorporated herein by reference. The ends of the braided tissue-derived particles may then be glued together using a fixation agent to prevent their unraveling, or they may be held together with a biocompatible polymer or metal band.

In an alternative embodiment, bone-derived particles are combined with a solvent to form a material. Exemplary solvents include water, lower alkanols, ketones, and ethers and mixtures of any of these or other materials. The material may then be extruded at an appropriate temperature and pressure to create a thread. Threads may also be produced by spinning, drawing, rolling, solvent-extruding, cutting or laser cutting from a sheet or bar stock. The material may alternatively be cast or molded into a solid sheet or bar stock and then cut into thin threads. These may be used immediately or woven into a mesh. Alternatively or in addition, they may be spliced, wrapped, plied, cabled, braided, woven, or some combination of these. The material may be shaped by thermal or chemical bonding, or both. In one embodiment, a portion of the solvent is removed from the material before extrusion.

Alternatively or in addition, the material may be cast as a slurry, extruded, or molded. A variety of materials processing methods will be well known to those skilled in the art. For example, the material may be solvent cast using a press such as a Carver press to spread the material into a film. Solvent evaporation will yield a porous film. Alternatively, the material may be compression molded into a film. The mesh size or porosity of the film will depend on the thickness of the film and the viscosity of the precursor and can be easily manipulated by one skilled in the art. Where elongated particles are used in an extruded aggregate, they will tend to be aligned roughly parallel to one another.

In an alternative embodiment, a thread of a biocompatible natural or synthetic material, for example, polylactide or collagen, may be coated with tissue-derived or other elements, for example, by dubbing. For example, a polymer fiber may be coated with an adhesive, for example, lecithin, and bone particles or other osteoconductive or osteoinductive fibrils allowed to adhere to the thread. The thread may then be twisted on itself or with a second or a plurality of similarly treated threads. Alternatively or in addition, the threads may be braided. The adhesive may be a lipid that is waxy at room temperature, for example, a di- or tri-glyceride that is solid at room temperature. Alternatively or in addition, the adhesive may be a phosphocholine or phosphatidylcholine. In some embodiments, the adhesive is a material that binds both the thread and the material that is used to coat the thread (e.g., bone particles) but that does not degrade either. Non-aqueous adhesives may improve the stability of the final aggregate as compared to aqueous adhesives.

Suitable fibers may be formed utilizing well known techniques, including braiding, plying, knitting, weaving, felting, that are applied to processing natural fibers, for example, cotton, silk, and synthetic fibers made from synthetic bioabsorbable polymers, such as poly(glycolide) and poly(lactic acid), nylon, cellulose acetate. See, Mohamed, American Scientist, 78: 530-541 (1990). In some embodiments, collagen thread is wound onto cylindrical stainless steel spools. The spools are then mounted onto the braiding carousel, and the collagen thread is then assembled in accordance with the instructions provided with the braiding machine. In one particular run, a braid was prepared of four collagen threads, which consisted of two threads of non-crosslinked collagen and two threads of crosslinked collagen. One skilled in the art will recognize that these techniques may be applied to the other fibrous materials described herein.

Fibers and more evenly dimensioned particles may also be plied into yarns using the same methods and same machinery known to those skilled in the art in plying threads made out of other material, such as cotton, polyester. Four collagen threads were twisted together. Three of the resultant 4-ply strands were then twisted together in the opposite direction, and then 5 of the resultant 12 ply strands were twisted in the opposite direction.

Elongated materials including multistranded materials, for example braids, plied yams, cables, may be knitted into tubular or flat fabrics by using techniques known to those skilled in the art of producing fabrics manufactured from other types of threads. Various biologically active substances can be incorporated in, or associated with, the braided, knitted, or woven materials. Particles and fibers and materials of these (including multistranded materials) may alternatively or additionally be assembled into a material by non-woven methods such as laying, needle-punching, and hooking (as for a rug). For example, a thread may be attached to another thread or a pressed film.

Regardless of the assembly method, the material shape, mesh size, cable thickness, and other structural characteristics, such as architecture, may be customized for the desired application. For example, where a two dimensional aggregate is used to retain a thixotropic material within a gap, a tight weave is preferred to prevent leakage. To optimize cell or fluid migration through the mesh, the pore size may be optimized for the viscosity and surface tension of the fluid or the size of the cells. For example, pore sizes on the order of approximately 100-200 μm may be used if cells are to migrate through the mesh. Mesh size may be controlled by physically weaving strands of the material by controlling the ratio of solvent to solids in a precursor material.

Cells may be seeded onto the material, or contained within it. In one embodiment, cells may be encapsulated in a matrix such as alginate or collagen gel and the capsules placed on the material. Seeded materials generally do not need to be incubated for long periods of time in solutions that could partially dissolve the binding agent. Instead, the capsules may be placed on the material or covering shortly before implantation. In another embodiment, cells are simply mixed with a gel which is then combined with the material. Alternatively, a material or covering may be cultured with cells before implantation. In one embodiment, thicker materials are used for culturing to increase mechanical integrity during implantation. Any class of cells, including connective tissue cells, organ cells, muscle cells, nerve cells, and stem cells, may be seeded onto the implant. In an exemplary embodiment, connective tissue cells such as osteoblasts, osteoclasts, fibroblasts, tenocytes, chondrocytes, and ligament cells and partially differentiated stem cells such as mesenchymal stem cells and bone marrow stromal cells are employed.

Covering Configurations

The shape, configuration, or form of the covering may be selected for particular applications. Such shape and configuration may include, for example, the basic shape of the covering (for example, a cylinder or a bag), whether the covering has a single or a plurality of compartments, and whether the covering includes attachment mechanisms. The covering (or delivery system) may be configured to conform to surrounding bony contours of the space in which it is placed.

In various embodiments, the covering may be formed of as a mesh and may comprise a woven material. The woven material may have varying degrees of permeability. It may be permeable, semi-permeable, or non-permeable. Permeability may be with respect to cells, to liquids, to proteins, to growth factors, to bone morphogenetic proteins, or other. In further embodiments, the material may be braided.

In alternative embodiments, the covering may comprise a substantially solid structure, such as a polymer structure with a chamber, or a spun cocoon.

The covering may have any suitable configuration. For example, the covering may be formed as a ring, a cylinder, a cage, a rectangular shape, a mesh, a suture-like wrap, a continuous tube, or other configuration. In specific embodiments, the covering may be formed as a thin tube designed to be inserted through catheters or an introducer tube, a rectangular shape designed to fit adjacent to spinal processes for posterolateral spine fusion, a cube like structure designed to fit between vertebral bodies or within cages for interbody spinal fusion, a tube-like shape where the ends are designed to be fitted onto nonunion long bone defects, relatively flat shapes designed to fill cranial or maxillofacial defects, rectangular structures designed for osteochondral defects, structures pre-shaped to fit around various implants (for example, dental, doughnut with hole for dental implants), or relatively elastic ring-like structures that will stretch and then conform to shapes (for example, rubber band fitted around processes). In an embodiment wherein the covering is formed as a cage, the cage may comprise a plurality of crossed filaments which define between them a series of openings for tissue ingrowth. Any of these shapes may be used for a covering comprising a plurality of compartments. For example, in a tubular embodiment, the tube may be formed into a plurality of compartments by tying a cord around the tube at one or more points, or by other suitable mechanism such as crimping, twisting, knotting, stapling, sewing, or other. The configuration of the covering may be determined by the substance to be provided within the covering. For example, if the substance to be contained comprises fibers, the covering may be formed as strings or sutures that are wrapped around the fibers.

Compartments

An osteogenic material delivery system 100 in accordance with one embodiment is depicted in FIGS. 1, 1A, 2 and 3. As shown in FIGS. 1, 1A, 2 and 3 delivery system 100 comprises a single compartment covering 102 having an elongated containment portion 104 for housing a substance for delivery to a surgical site. Elongated containment portion 104 has a first and second end 106, 108. Elongated containment portion 104 comprises a length, width and cross section which may vary depending on the application for the covering. The cross section can be tubular or cylindrical and in alternative embodiments, any cross-sectional shape, such as a generally circular, oval, rectangular, generally square, generally star, or any other suitable shape may be used. In the embodiments shown in FIGS. 1, 1A, 2, and 3 the coverings 102 comprise a mesh material and the delivery system 100 can be a mesh bag. Within these coverings or mesh bags, there is provided a particulated substance such as milled bone or DBM particles/fibers, wherein the ratio of DBM fibers to DBM chips is about 30:60.

In various embodiments, the covering may be configured to facilitate placement of graft material in the covering. For example, in FIG. 1A, first end 106 of elongated containment portion 104 defines at least one access port 110 configured for receiving a first needle 112. The first needle 112 has an elongated stem connected to a first syringe like device 114 containing bone graft material or other biocompatible material such as live cells or growth factors. The needle can be pushed completely across elongated containment portion 104. The needle can be a length of from about 50 to 150 mm in length, for example, about 65 mm to about 200 mm. The thickness of the needle can be from about 0.05 to about 1.655. The gauge of the needle can be about 14 gauge to about 18 gauge or about 22 gauge. In one embodiment, the needle is a customized cannula having a diameter of from about 3 mm to about 5 mm.

As plunger 115 of syringe 114 is pushed towards the needle and extracted out of the mesh bag 102 the bone graft material is expelled and forced to mix with, surround and coat the DBM particles/fibers with bone graft material so that bone formation can be induced throughout the graft rather than just along the surface of the DBM containing mesh bag.

In another embodiment illustrated in FIG. 2, the second end 108 of elongated containment portion 104 defines a second port 116 configured to receive a second needle 118. The second needle 118 has an elongated stem and is configured to connect to a second bone graft material delivery means such as a syringe containing bone graft material or other suitable biocompatible material for release into the containment portion 104.

A covering as provided herein may further comprise other cavities or thru holes as shown in FIG. 3. In some embodiments any other surface for example a top surface of covering 102 can define at least one or more cavities or thru holes for easy access to the elongated containment portion 104 of the delivery systems provided herein. FIGS. 3 and 4A illustrate a top view and end view, respectively, of an embodiment having three thru holes 120 which can be utilized to fill the elongated containment portion with autologous bone or growth factors thereby increasing the exposure of DBM particles/fibers to osteogenic cells and allowing the DBM cytokines to signal the autologous osteogenic cells to begin forming new bone or to boost the osteoactivity of the weakly osteoinductive DBM already present in covering 102. In various embodiments, the thru holes present in the elongated containment portion of the delivery systems described herein may have the same size or be of different sizes, generally having a diameter from about 1 mm to about 10 mm, or from about ⅓ to about ⅔ the width of the containment portion, or, in another embodiment, from about ⅕ to about the complete length of the containment portion. The ports (110 and 116) can be self sealed, sealed by heat, adhesion, sutured, or have a flap that pulls down over the opening. In one embodiment, the port size is from about 6 mm down to the diameter of a 22 gauge needle.

In the embodiments shown in FIGS. 1 to 10 both ends 106 and 108, 206 and 208, 228 and 230, respectively can be sealed either self sealed or sealed by heat, adhesion or stitches. One or both ends 106, 108, 206 and 208, 228 and 230 may contain an attachment or coupling mechanism (not shown) to attach the covering to skeletal or soft tissue proximate to a surgical site. Any suitable attachment mechanism can be used, such as a tab, loop, tack or other structure adapted for attachment at the site. Also, for example, a covering may include a hook-and-eye (Velcro) portion.

In alternative embodiments, covering 102 may comprise a plurality of compartments as illustrated in FIGS. 4 to 10. FIG. 4 shows a multi compartment embodiment 200 of covering 202 having an elongated containment portion 204 separated into three distinct compartments 222, 224 and 226 by perforations or other types of temporary or permanent boundaries or partitions 210. Compartment 204 has a first and second end 206, 208 and compartments 222, 224 and 226 extend substantially along the entire length of elongated containment portion 204, one over the other.

In various embodiments, the materials for each compartment may have different release profiles, different porosities, and other different characteristics. Selection of materials, positioning of the compartments, and other factors relating to the first, second or third compartments may be chosen to achieve simultaneous or sequential delivery or release of a substance or substances. For example, a first substance may be provided in the first compartment, a second substance may be provided in the second compartment and a third substance may be provided in the third compartment. In some embodiments, an osteoinductive substance may be placed in a compartment generally adjacent tissue being treated as implanted and an osteoconductive substance may be placed in a compartment not adjacent tissue being treated. Release rates for the materials provided in a first compartment, and second compartment may be different from each other and from the material placed in a third compartment. In some embodiments as further illustrated in FIGS. 7 to 10, at least one of the compartments may be unfilled at the time of surgery and autograft or other material may be provided therein in the operating room or at the surgical site.

FIG. 5 is another exemplary multi compartment embodiment of covering 202 having an elongated containment portion 204 containing a substance for delivery separated into compartments 232 to 244. Covering 202 also includes a first and second tapered ends 228 and 230. As in other embodiments discussed herein, ends 228 and 230 may be sealed and attached or coupled to an attachment mechanism (not shown). In FIG. 5 compartments 232 to 244 are situated side by side and each is separated by barrier 250. In FIG. 5, barriers 250 may be perforated for separation from each other, or may be other kinds of temporary or permanent boundaries or partitions. In some embodiments, the compartments may be separated by a seal, may communicate there between, may be substantially separate, or may be otherwise divided with respect to other multi-compartment embodiments. The barriers 250 may be temporary or may be substantially permanent, namely remaining for the life of the covering 202. In some embodiments, a temporary barrier may be a sheet or a masking agent.

FIG. 6 illustrates a multi compartment embodiment of covering 202 having an elongated containment portion 204 and a first and second tapered ends 228 and 230 and three compartments 252, 254 and 256 extending substantially along the entire length of the elongated containment portion 204, one over the other. The three compartments may be separated by a seal, may communicate there between, may be substantially separate, or may be otherwise divided with respect to other multi-compartment embodiments.

As in embodiment illustrated in FIG. 4, the materials for each compartment shown in FIG. 6 may have different release profiles, different porosities, and other different characteristics. Selection of materials, positioning of the compartments, and other factors relating to the first, second or third compartments may be chosen to achieve simultaneous or sequential delivery or release of a substance or substances. For example, a first substance may be provided in the first compartment, a second substance may be provided in the second compartment and a third substance may be provided in the third compartment.

In some embodiments, the compartments have barriers between them that can be the same or different porosity and allow bioactive agents, cells and/or bone material to cross in and out of the barrier. In some embodiments, the barrier and/or compartments can be biodegradable and degrade at different rates.

In some embodiments, other delivery systems provided herein include multi compartment mesh bag designs for placing autologous milled bone or growth factors in close proximity to DBM particles configured to prevent the migration of these bioavailable particles away from the DBM particles/fibers therefore increasing the activity of the weakly osteoinductive DBM.

FIGS. 8 to 10 illustrate various embodiments wherein some of the compartments are at least partly filled with graft material and/or DBM. For example, compartments 260, 262, 264, 266 and 268 of covering 204 as manufactured are initially filled with DBM while compartments 270, 272, 274, 276 and 278 are initially empty but may subsequently be filled with autologous milled bone or growth factor utilizing access ports or other cavities (not shown) available in these compartments.

In certain other embodiments only one end 280 of the covering or mesh bag 204 is sealed while the other is open to provide easy access for mixing DBM particles/fibers with autologous milled bone or growth factor before or during the surgical procedure. Subsequently, the covering or mesh bag can be closed by various mechanisms including draw strings 284 as shown in FIGS. 12 and 13, sutured or heat seal closed. The draw string can be sequentially or diagonally stitched or in any other pattern configured to close the mesh bag after all the materials were added and prior to placing at a surgical site.

In other embodiments the covering or mesh bag can be provided with a funnel 280 pre-inserted into an existing port to facilitate filling during surgery as shown in FIG. 14. The covering or mesh bag shown in FIG. 14 can be configured to fit into a stand (not shown) to hold it upright during the filling step.

For both single and multi-compartment coverings, the covering may be closed after filling substances. Further, the covering may be left substantially open with one or more unsealed ends. Accordingly, the covering may be provided in an unfilled, unsealed state. After a substance for delivery is placed in the covering, the covering may be permanently or temporarily closed. Permanent closure may be, for example, by heat sealing, stitching, adhesion, or other methods. Temporary closure may be by tying, fold lock, or cinching. A temporarily closed covering can be opened without damaging to the covering during surgical implantation to add or remove substances in the covering. In some embodiments, the compartments can be unfilled at manufacture and configured to be filled prior to or during the surgical procedure.

Attachment Mechanisms

Generally, any combination of mechanical, physical, chemical, or biological attachment mechanisms may be used. The covering may be configured with structures to permit attachment at the surgical site, such as to skeletal tissue or to soft tissue structures, or for attachment to other coverings, or for attachment to adjacent implantable medical devices or products (such as a rod or screw or cross-brace of a pedicle screw fixation system, a hip prosthesis, a bone plate, and the like). Generally, the attachment mechanism may be used to retain the covering at the surgical site and any mechanisms capable of doing so may be used. The attachment may be to bone or to adjacent tissues such as muscle, tendon, or ligament. Where the covering retains a bone graft substance, the covering may be held in a relatively stable position relative to bone (or relative to the surgical site or surgical defect) to promote bone growth. Accordingly, in some embodiments, the delivery system may be suitable for assisting in attaching tendons, artificial tendons, or ligaments to bone or other structure.

Chemical attachment mechanisms may comprise, for example, a bioadhesive or glue, cement, tape, tissue adhesives, or similar mechanism. Chemical attachment mechanisms may further comprise mechanisms that facilitate cross-linking. In further embodiments, attachment mechanisms such as crimping, welding, soldering, or brazing may be used. Further, attachment may be achieved via friction.

In some embodiments, biological attachment may be via mechanisms that promote tissue ingrowth such as by a porous coating or a hydroxyapatite-tricalcium phosphate (HA/TCP) coating. Generally, hydroxyapatite bonds by biological effects of new tissue formation. Porous ingrowth surfaces, such as titanium alloy materials in a beaded coating or tantalum porous metal or trabecular metal may be used and facilitate attachment at least by encouraging bone to grow through the porous implant surface. These mechanisms may be referred to as biological attachment mechanisms.

Any of the various attachment mechanisms may be provided as part of the covering or may be supplied separately. In various embodiments, the attachment mechanisms may be integral to the covering. Alternatively, the attachment mechanisms may be secured to the covering, for example, by stitching, welding, crimping, or other. The attachment mechanisms may have any suitable geometric configuration and may optionally include apertures for receiving other components for coupling in vivo, such as an aperture for receiving a screw. Thus, for example, an attachment mechanism may be provided configured for receiving an anchor for fixation to bone. Generally, any number of attachment mechanisms may be provided at any suitable location on the covering.

The attachment mechanisms may be manufactured of the same material as the portion of the covering to which it is coupled or may be manufactured of a different material from the portion of the covering to which it is coupled. The attachment mechanism may be resorbable or nonresorbable. The material of the attachment mechanism may be selected to allow anchoring the covering to an adjacent covering having a complementary attachment mechanism or to another structure. In various embodiments, the attachment mechanism may comprise, allograft, synthetic materials, demineralized bone, nondemineralized bone, other material, or combinations of these. The shape and size of the attachment mechanism may be selected based on application.

In some embodiments, the covering may be tubular and have threaded ends such that the ends may be threaded with a reciprocal thread of a further device or implant. For example, the covering may be used with interference screws. In some embodiments, the covering may include extensions or tabs that may be used for wrapping around or suturing to the surgical site. Alternatively, the covering may be sutured directly to the surgical site. The ends of the covering may be presealed or may be sealed after introduction of contents. Sealing may be done by using adhesives, heating, solvent treatment, suturing, knotting, or any other means.

The substance may be packed in the covering at any suitable density. For some applications, the substance may be loosely packed in the covering to enhance manipulability. In some embodiments, the material may be packed in the covering such that the covering retains flexibility and may be folded over itself. In other applications, the substance may be tightly packed in the covering to provide a relatively stiff delivery system, and it may be weight bearing. In some embodiments, the covering may be configured to facilitate placement of graft material in the covering as was illustrated in FIGS. 1-13 described herein.

Substance for Delivery by Covering

A substance is provided in the covering, before or during surgery (as described below), for delivery in vivo. Generally, the substance or material may be homogenous or heterogeneous. The substance or material may be selected to exhibit certain gradients. In some embodiments, the substance may be a bioactive agent that exhibits a gradient to guide, lure, or attract cells along a pathway. Such gradient may comprise a cell gradient, a cell type gradient (for example transitioning from bone cells to cartilage cells or transitioning from bone cells to tendon cells), a gradient of conductivity, or a gradient of density/porosity. In some embodiments, the substance or material may comprise a sequence of ingredients.

The covering may be used to deliver a substance comprising any suitable biocompatible material. In specific embodiments, the covering may be used to deliver a bioactive agent, which comprises surface demineralized bone chips (cortical or cancellous), optionally of a predetermined particle size, demineralized bone fibers, optionally pressed, and/or allograft material. For example, the bioactive agent can be, in certain embodiments, DBM where the ratio of DBM fibers to DBM chips is about 30:60.

For embodiments wherein the substance is bioactive agent, the substance may be autogenic, allogenic, xenogenic, transgenic, or combinations of these. Each of these tissue types includes any tissue of bone origin, connective tissue origin, or any collagen containing material including organ tissues. Other suitable materials that may be positioned in the covering include, for example, protein, hormones, nucleic acid, carbohydrate, lipids, collagen (autograft, allograft, or xenograft from musculoskeletal or organ systems), allograft bone, autograft bone, cartilage stimulating substances, allograft cartilage, TCP, TCP/calcium sulfate, calcium carbonate, calcium phosphates, bioactive glasses, glass ceramics, magnesium phosphates, phosphates containing any biocompatible metal ion, porous implants of all types including trabecular metal, biocompatible metals including stainless steel, cobalt-chrome, titanium, titanium alloys, polymers such as polylactic acid, polyglycolic acid, polycaprolactone, polyglycolide-co-caprolactone, polyethylene oxide, polypropylene oxide, polyglycolide-co-trimethylene carbonate, poly(lactic-co-glycolic acid), poly-L-lactide, polyethylene glycol, polyetheretherketones, polyurethanes, polyethers of all types, poly ethylene terephthalte, polyethylene, polypropylene, Teflon, chondroitin sulfate, hyaluronic acid and its salts, chitosan and derivatives, natural polymers such as silk, collagen, polysaccharides, polyhydroxyalkanoates, polymers combined with bone or collagen or both from any source (allograft, xenograft, transgenic, autograft), hydroxyapatite, calcium sulfate, polymer, nanofibrous polymers, growth factors, carriers for growth factors, growth factor extracts of tissues, demineralized bone matrix, dentine, bone marrow aspirate, bone marrow aspirate combined with various osteoinductive or osteoconductive carriers, concentrates of lipid derived or marrow derived adult stem cells, umbilical cord derived stem cells, adult or embryonic stem cells combined with various osteoinductive or osteoconductive carriers, transfected cell lines, bone forming cells derived from periosteum, combinations of bone stimulating and cartilage stimulating materials, committed or partially committed cells from the osteogenic or chondrogenic lineage, platelets, activated platelets, antibiotics, substances with antimicrobial properties, or combinations of any of the above. In accordance with one embodiment, the substance is a bone matrix composition such as described in U.S. patent application Ser. No. 12/140,044 and U.S. Patent Publications Nos. 2007/0098756 and 2007/0110820 all for Bone Matrix Compositions and Methods, herein incorporated by reference in their entireties. Suitable materials for preparing biocomposites for placement in the covering are disclosed in U.S. Patent Publication Nos. 2007/0191963, 2006/0216323, and 2005/0251267, U.S. Pat. Nos. 6,696,073, 6,478,825, 6,440,444, and 6,294,187, all herein incorporated by reference in their entireties for all purposes.

In some embodiments, the substance or material for delivery may comprise a biodegradable polyester such as poly(lactic acid) (PLA), poly(glycolic acid) (PGA), poly(lactic-co-glycolic acid) (PLGA), or polyhydroxyalkanoates (polyhydroxybutyrates and polyhydroxyvalerates and copolymers), polysaccharides, polyhydroxyalkanoates, polyglycolide-co-caprolactone, polyethylene oxide, polypropylene oxide, and polyglycolide-co-trimethylene carbonate. In some embodiments, poly(ethylene glycol) (PEG) may be incorporated into the biodegradable polyester to add hydrophilic and other physico-chemical properties to enhance drug delivery. In some embodiments, composites of allograft bone and biodegradable polymers (for example, PLEXUR® products available from Osteotech) may be delivered by the covering.

In some embodiments, the substance may be pressed before placement in the covering. A substance provided within the covering may be homogenous, or generally a single substance, or may be heterogeneous, or a mixture of substances. In some embodiments, the substance may be designed to expand in vivo. U.S. Patent Publications No. 2008/0091270 describes an osteoimplant that expands in vivo and is herein incorporated by reference in its entirety. Such an embodiment may be used to fill a space and create contact with congruent surfaces as it expands in vivo, for example for interbody fusion. Thus, in some embodiments, the delivery system may be used in the disc space, between implants, or inside a cage. In some embodiments, the substance may include a natural and/or synthetic expandable material. The expandable material may comprise bone particles, a polymer, a hydrogel, a sponge, collagen, or other material. In various embodiments, the expandable material comprises bone allograft comprising demineralized bone particles, and the demineralized bone particles may be a blend of cortical and cancellous bone. For example, the expandable material may comprise demineralized cortical fibers and demineralized cancellous chips, wherein the demineralized cancellous chips may create a healthy matrix for the incorporation of new bone and add advanced expansion characteristics.

In addition to bone particles, an expandable polymer, a collagen sponge, compressed and/or dried hydrogels, or other materials may be used. In addition to expansion properties, the material may exhibit osteoinductive and/or osteoconductive properties. For example, cancellous bone particles may exhibit osteoconductive properties while demineralized cortical bone particles may exhibit osteoinductive properties.

The expandable material may be compressed during formation to aid in subsequent expansion. Generally, increased compression leads to increased expansion characteristics in the osteoimplant. Compressed materials and certain non-compressed materials may be constrained such that, absent the constraint, the material is free to expand. A constrained material is one that embodies energy, such as a bent, spring-loaded, or coiled material, or any other material that is artificially prevented from expanding or conforming to its natural configuration. The expandable material may include a covering material that partially or wholly surrounds the material. The covering material may be provided also expand as the expandable material expands.

Expansion may be activated in any suitable manner. For example, expansion may be activated by exposure to air, water, blood, heat, removal of a constraint, or otherwise. In one embodiment, the expandable material may be provided compressed and dried. Upon exposure to liquid in vivo, the expandable material may expand. In another embodiment, the expandable may be compressed and at least partially constrained by a covering material. Upon exposure to liquid in vivo, the covering material may expand or disintegrate, as the expandable material expands. The expandable material may expand as a function of time. In yet another embodiment, the expandable material may have a first state at approximately 60° F. and an expanded state at approximately 98° F. such that, upon implantation in vivo and exposure to body heat, the expandable material may expand. In a further embodiment, the expandable material may be vacuum-sealed during manufacture and, when unsealed and exposed to air, the expandable material may expand.

The covering retains the substance in place by pressure against the covering. The covering thus may, in some embodiments, maintain particles of substance in close proximity (for example, where the covering retains a substance comprising bone particles). Generally, the ratio of covering material to substance for placement within the covering may be low. For example, in some embodiments, the ratio of covering material to substance, by weight, may be approximately 1:1,000, 1:100, 1:50, 1:25, 1:1, or any suitable ratio that may be higher or lower than these.

In some embodiments the substance delivered by the covering may include or comprise an additive such as an angiogenesis promoting material or a bioactive agent. It will be appreciated that the amount of additive used may vary depending upon the type of additive, the specific activity of the particular additive preparation employed, and the intended use of the composition. The desired amount is readily determinable by one skilled in the art. Angiogenesis may be an important contributing factor for the replacement of new bone and cartilage tissues. In certain embodiments, angiogenesis is promoted so that blood vessels are formed at an implant site to allow efficient transport of oxygen and other nutrients and growth factors to the developing bone or cartilage tissue. Thus, angiogenesis promoting factors may be added to the substance to increase angiogenesis. For example, class 3 semaphorins, e.g., SEMA3, controls vascular morphogenesis by inhibiting integrin function in the vascular system, Serini et al., Nature, (July 2003) 424:391-397, incorporated by reference herein, and may be included in the recovered hydroxyapatite.

In accordance with some embodiments, the substance may be supplemented, further treated, or chemically modified with one or more bioactive agents or bioactive compounds. Bioactive agent or bioactive compound, as used herein, refers to a compound or entity that alters, inhibits, activates, or otherwise affects biological or chemical events. For example, bioactive agents may include, but are not limited to, osteogenic or chondrogenic proteins or peptides; demineralized bone powder; collagen, insoluble collagen derivatives, etc., and soluble solids and/or liquids dissolved therein; anti-AIDS substances; anti-cancer substances; antimicrobials and/or antibiotics such as erythromycin, bacitracin, neomycin, penicillin, polymycin B, tetracyclines, biomycin, chloromycetin, and streptomycins, cefazolin, ampicillin, azactam, tobramycin, clindamycin and gentamycin; bacteriaphages; immunosuppressants; anti-viral substances such as substances effective against hepatitis; enzyme inhibitors; hormones; neurotoxins; opioids; hypnotics; anti-histamines; lubricants; tranquilizers; anti-convulsants; muscle relaxants and anti-Parkinson substances; anti-spasmodics and muscle contractants including channel blockers; miotics and anti-cholinergics; anti-glaucoma compounds; anti-parasite and/or anti-protozoal compounds; modulators of cell-extracellular matrix interactions including cell growth inhibitors and antiadhesion molecules; vasodilating agents; inhibitors of DNA, RNA, or protein synthesis; anti-hypertensives; analgesics; anti-pyretics; steroidal and non-steroidal anti-inflammatory agents; anti-angiogenic factors; angiogenic factors and polymeric carriers containing such factors; anti-secretory factors; anticoagulants and/or antithrombotic agents; local anesthetics; ophthalmics; prostaglandins; anti-depressants; anti-psychotic substances; anti-emetics; imaging agents; biocidal/biostatic sugars such as dextran, glucose, etc.; amino acids; peptides; vitamins; inorganic elements; co-factors for protein synthesis; endocrine tissue or tissue fragments; synthesizers; enzymes such as alkaline phosphatase, collagenase, peptidases, oxidases, etc.; polymer cell scaffolds with parenchymal cells; collagen lattices; antigenic agents; cytoskeletal agents; cartilage fragments; living cells such as chondrocytes, bone marrow cells, mesenchymal stem cells; natural extracts; genetically engineered living cells or otherwise modified living cells; expanded or cultured cells; DNA delivered by plasmid, viral vectors, or other means; tissue transplants; autogenous tissues such as blood, serum, soft tissue, bone marrow, etc.; bioadhesives; bone morphogenic proteins (BMPs); osteoinductive factor (IFO); fibronectin (FN); endothelial cell growth factor (ECGF); vascular endothelial growth factor (VEGF); cementum attachment extracts (CAE); ketanserin; human growth hormone (HGH); animal growth hormones; epidermal growth factor (EGF); interleukins, e.g., interleukin-1 (IL-1), interleukin-2 (IL-2); human alpha thrombin; transforming growth factor (TGF-beta); insulin-like growth factors (IGF-1, IGF-2); parathyroid hormone (PTH); platelet derived growth factors (PDGF); fibroblast growth factors (FGF, BFGF, etc.); periodontal ligament chemotactic factor (PDLGF); enamel matrix proteins; growth and differentiation factors (GDF); hedgehog family of proteins; protein receptor molecules; small peptides derived from growth factors above; bone promoters; cytokines; somatotropin; bone digesters; antitumor agents; cellular attractants and attachment agents; immuno-suppressants; permeation enhancers, e.g., fatty acid esters such as laureate, myristate and stearate monoesters of polyethylene glycol, enamine derivatives, alpha-keto aldehydes, etc.; and nucleic acids.

In certain embodiments, the bioactive agent may be a drug. In some embodiments, the bioactive agent may be a growth factor, cytokine, extracellular matrix molecule, or a fragment or derivative thereof, for example, a protein or peptide sequence such as RGD. A more complete listing of bioactive agents and specific drugs suitable for use in the present invention may be found in “Pharmaceutical Substances: Syntheses, Patents, Applications” by Axel Kleemann and Jurgen Engel, Thieme Medical Publishing, 1999; the “Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals”, Edited by Susan Budavari et al., CRC Press, 1996; and the United States Pharmacopeia-25/National Formulary-20, published by the United States Pharmacopeia Convention, Inc., Rockville Md., 2001.

In some embodiments the drug can be a statin. Examples of a useful statin for treatment of pain and/or inflammation include, but is not limited to, atorvastatin, simvastatin, pravastatin, cerivastatin, mevastatin, velostatin, fluvastatin, lovastatin, rosuvastatin and fluindostatin (Sandoz XU-62-320), dalvastain, eptastatin, pitavastatin, or pharmaceutically acceptable salts thereof or a combination thereof. In various embodiments, the statin may comprise mixtures of (+)R and (−)-S enantiomers of the statin. In various embodiments, the statin may comprise a 1:1 racemic mixture of the statin. Anti-inflammatory agents also include those with anti-inflammatory properties, such as, for example, amitriptyline, carbamazepine, gabapentin, pregabalin, clonidine, or a combination thereof.

Unless otherwise specified or apparent from context, where this specification and the set of claims that follows refer to a drug (e.g., an anti-inflammatory agent, analgesic, or the like) this disclosure is also referring to a pharmaceutically acceptable salt of the drug including stereoisomers. Pharmaceutically acceptable salts include those salt-forming acids and bases that do not substantially increase the toxicity of the compound. Some examples of potentially suitable salts include salts of alkali metals such as magnesium, calcium, sodium, potassium and ammonium, salts of mineral acids such as hydrochloric, hydriodic, hydrobromic, phosphoric, metaphosphoric, nitric and sulfuric acids, as well as salts of organic acids such as tartaric, acetic, citric, malic, benzoic, glycollic, gluconic, gulonic, succinic, arylsulfonic, e.g., p-toluenesulfonic acids, or the like.

In one embodiment of a covering comprising two compartments, a first growth factor may be provided for delivery by the first compartment and a second growth factor may be provided for delivery by the second compartment. The first and second growth factors may be provided with other substances. The first and second growth factors may be selected (and placed in respective compartment for positioning in vivo) based on desired characteristics of the growth factor. For example, an angiogenic growth factor may be provided in the first compartment and an osteoinductive growth factor may be provided in the second compartment. Similarly, the substance delivered by the first compartment and the substance delivered by the second compartment may be selected based on desired characteristics of the compartment according to its placement in vivo. Thus, for example, one compartment may have a substance that is substantially osteoclast stimulating while another compartment may have a substance that is substantially osteoblast stimulating.

In one embodiment, demineralized bone fibers may be provided in the first compartment and surface demineralized bone chips may be provided in the second compartment. In this embodiment, the demineralized bone fibers may generally provide osteoinductive characteristics and the surface demineralized chips may generally provide osteoinductive and/or osteoconductive characteristics. In use, the covering may be laid flat on the transverse process and positioned such that the first compartment, holding the demineralized bone fibers, is nearest the vertebral body and the second compartment, holding the surface demineralized bone chips, is farther from the vertebral body, or the compartments may be positioned in any other desired configuration. In another embodiment, a covering may comprise first and second compartments wherein autograft may be placed in one of the compartments prior to placement of the covering in vivo, described more fully below. In other embodiments, three or more compartments may be used, as appropriate for the materials being delivered and the application of the compartmented implant. More than one substance may be provided within a single compartment. Such mixture of substances within a single compartment may be a substantially uniform mix or may be a plurality of substances placed in the compartment separately such that they are substantially unmixed. When multiple compartments are used, each compartment may contain one or more substances. Exemplary substances that may be provided in one or more compartments of the delivery system include cells from the osteogenic precursors, growth factors, angiogenic factors and other active proteins including bone morphogenic proteins, and cellular scaffolding materials of natural or synthetic origin, antibiotics, and other substances described below.

Generally, any suitable substance or material may be delivered using coverings as provided herein. Such substances may include bone, cartilage, tendon, ligament, muscle, skin, nerve, collagen, calcium sulfate (CaSO₄), calcium phosphate (CaPO₄), βTCP, hydroxyapatite, bioglass, silicon-containing calcium phosphates, cells, autograft, or other.

In some embodiments, a particulate substance may be delivered by the covering. For example, the covering may be used to deliver a particulate bone graft.

Growth factors or other active substances may be delivered by the covering. Active substances may include, for example, growth factors such as BMP-2 (Infuse) and/or other growth proteins, as well as drugs, for example, antibiotics. In some embodiments, a carrier for the growth factors or other active substances may be incorporated into the delivery system.

It will be apparent to those skilled in the art that various modifications and variations can be made to various embodiments described herein without departing from the spirit or scope of the teachings herein. Thus, it is intended that various embodiments cover other modifications and variations of various embodiments within the scope of the present teachings. 

What is claimed is:
 1. A delivery system comprising a covering having at least one compartment, a bone material disposed within the covering, an access port coupled to the at least one compartment and contacting or adjacent to the bone material, the at least one compartment configured to receive a bioactive agent from the access port for mixing with the bone material prior to delivery of the delivery system to a surgical site.
 2. A delivery system according to claim 1, wherein the covering comprises a porous mesh and the delivery system comprises implantable material.
 3. A delivery system according to claim 1, wherein the at least one compartment comprises a demineralized bone matrix material as the bone material and the bioactive agent contacts the demineralized bone matrix material when the bioactive agent is introduced into through the access port.
 4. A delivery system according to claim 1, wherein the at least one compartment comprises an elongated containment portion having a first end and second end opposite each other, wherein at least one end defines the access port.
 5. A delivery system according to claim 1, wherein the at least one compartment further comprises a top surface, wherein the top surface comprises the access port or at least a through hole.
 6. A delivery system according to claim 5, wherein the access port or through hole is self sealing or sealable by sutures, heat or a combination thereof.
 7. A delivery system according to claim 1, wherein the access port is configured to receive a needle connected to a means for delivering an osteogenic material.
 8. A delivery system according to claim 7, wherein the means for delivering an osteogenic material is a syringe containing an osteogenic material and the syringe comprises a plunger.
 9. A delivery system according to claim 8, wherein the plunger is configured to release the osteogenic material into the at least one compartment as the plunger is pushed toward the needle and the needle is extracted out of the elongated containment portion of the delivery system.
 10. A delivery system according to claim 4, wherein the elongated containment portion comprises a first end and a second end, wherein either the first end or the second end or both ends of the elongated containment portion are configured to be sealed by a sealing mechanism comprising a draw string, sutures, heat seals or a combination thereof.
 11. A delivery system according to claim 4, wherein either the first end or the second end or both ends of the elongated containment portion are configured to receive a funnel adapted to channel bone graft material into the containment portion of the delivery system.
 12. A delivery system according to claim 11, wherein the delivery system further comprises a stand for use in supporting the elongated containment portion while it receives bone graft material.
 13. A delivery system according to claim 1, wherein the bone material is demineralized bone matrix material comprising particles and fibers of demineralized bone.
 14. A delivery system according to claim 1, wherein the bioactive agent comprises protein, bone morphogenetic proteins, carbohydrate, lipids, collagen, allograft bone, autograft bone, tricalcium phosphate, hydroxyapatite, growth and differentiation factors, bone promoting substance, carriers for growth factors, growth factors extracts of tissue, bone marrow aspirate, concentrates of lipid derived or marrow derived adult stem cells, umbilical cord derived stem cells, committed or partially committed cells from osteogenic or chondrogenic lineage, antimicrobials, antibiotics, statins, or combinations thereof.
 15. A delivery system according to claim 4, wherein the elongated containment portion has a cross sectional shape that is generally circular or generally oval.
 16. A delivery system according to claim 4, wherein the elongated containment portion has a tubular, rectangular, cube or mesh bag shape.
 17. A delivery system according to claim 4, wherein the elongated containment portion comprises at least a first compartment and a second compartment.
 18. A delivery system according to claim 17, wherein the at least first and second compartments each extend from the first to the second end of the elongated containment portion.
 19. A delivery system according to claim 18, wherein the at least first and second compartments are arranged side by side or the at least first compartment is arranged over the at least second compartment.
 20. A delivery system according to claim 19, wherein the at least first and second compartments are separated by a barrier, wherein each barrier is biodegradable. 